[JSON API] ED doesn't consider links in the compound documents

[lancedikson]

It seems that ED doesn't recognize links when data exists as well in the response from the server. The example of a buggy response from server:

{
  "data": {
  	...
  },
  "included": [
    {
      "type": "blog-posts",
      "id": "1",
      "attributes": {
        "title": "Lorem"
      },
      "relationships": {
        "comments": {
          "links": {
            "related": "/api/blog-posts/1/comments"
          },
          "data": [
            {
              "type": "comments",
              "id": "1"
            },
            {
              "type": "comments",
              "id": "2"
            },
            {
              "type": "comments",
              "id": "3"
            }
          ]
        }
      }
    }
  ]
}

In that case, ED is trying to send requests to /api/comments/1 ignoring the links.related attribute. But, seems that it should recognize that kind of links according to the specification. Also, I created a discussion on the JSON API forum.

[stefanpenner]

This seems quite close to the test scenario provided in #5147 can you confirm that is the same scenario? If so, #5147 fixes it. If not, if you can provide a failing test, I can investigate.

[andrewfan]

Hey, @stefanpenner @lancedikson, I think links.related still does not work, I did not check the whole flow of serialization to understand if links from response are properly stored somewhere, but I checked https://github.com/emberjs/data/blob/master/addon/-private/adapters/build-url-mixin.js#L55. buildURL method is called for every API operation and it does not have any logic for handling links. @stefanpenner do you know if this feature will be supported in the near future?

[runspired]

This is resolved by #5410 🎉